In the manufacture of bevel and hypoid gears it is well known to utilize face mill type cutters in both generating and non-generating gear cutting processes. In face mill cutters, cutting blades are arranged in the cutter head such that one tooth slot is formed with each cutting cycle (e.g. plunge, or feed-in and roll) of the cutter. The cutter must be withdrawn and the workpiece indexed to the next tooth slot position in order to form the next tooth slot. With face milling, all cutting blades of the face mill cutter pass through the tooth slot during the cycle until the desired slot geometry (and hence, tooth flank geometry) is formed.
Face milling tools include a plurality of blades projecting from a front face or periphery of a cutter head wherein the cutting blades are arranged in one or more concentric circles about an axis of rotation of the cutter head. Cutting blades may be of the type commonly referred to as stick-type or bar blades made of a length of bar stock (for example, U.S. Pat. No. 4,137,001 to Fountain; U.S. Pat. No. 4,575,285 to Blakesley; U.S. Pat. No. 6,120,217 to Stadtfeld et al.; or U.S. Pat. No. 3,760,476 to Kotthaus). Cutting blades may also be of the form-relieved type (for example, U.S. Pat. No. 3,192,604 to Whitmore or U.S. Pat. No. 3,268,980 to Blakesley et al.). Either type may be made of suitable material such as high speed steel (HSS) or carbide and the blades may have one or more surfaces coated with wear enhancing coatings such as TiN, TIAlN, AlTiN, etc. as is known by the artisan.
Typically in face mill cutters, a set of “inside” blades for cutting convex flanks of work gear teeth are arranged at a first radius from the cutter head axis, and a set of “outside” blades for cutting concave flanks within the same tooth space are arranged at a second larger radius. Examples of this type of cutter can be seen in U.S. Pat. No. 2,024,494 to Wildhaber or U.S. Pat. No. 4,137,001 to Fountain. In some cutters, separate bottom blades are included to cut the bottom of a tooth slot (e.g. U.S. Pat. No. 3,760,476 to Kotthaus) while in other cutters, the inside and outside cutting blades include cutting portions which also cut at the bottom of the tooth slot (for example, U.S. Pat. No. 4,278,370 to Spear). Alternatively, cutting blades that cut the convex side, concave side and the bottom of a tooth slot (i.e. the entire tooth slot) may also be utilized. Examples of this type of cutter are shown in U.S. Pat. No. 1,236,834 to Gleason; U.S. Pat. No. 1,667,299 to Wildhaber; or WO 2004/103624 to Ribbeck.
In producing gears with cutters having inside and outside cutting blades, uneven wear of the cutting blades is of significant concern as certain areas of the blades experience wear and break down earlier than other areas. With cutters having blades that cut the entire tooth slot, large chips tend to form which can result in chip flow problems and truing of such cutters cannot be accomplished since repositioning a cutting blade to true one cutting side of the cutting blade will also affect the position of other cutting side likely causing the other side to shift out of an optimal cutting position.